A method of erasing colors of a toner image formed on a recording medium such as paper and reusing the recording medium such as paper is very effective from the viewpoints of environmental protection and economy by reducing the use amount of the recording medium.
There is proposed a method of obtaining an electrophotographic toner by aggregating and fusing a fine particle containing a leuco dye, a developer and/or a color erasing agent and a toner binder.
According to this method, when the color erasing agent is used in the fine particle, a so-called irreversible color erasing characteristic such that color restoration cannot be achieved can be obtained. However, when color erasing is performed in a manufacturing step of a fine particle and a toner, or in a fixing step at the image formation, the application cannot be achieved.
If the color erasing agent is not used in the fine particle, when color erasing is performed in a manufacturing step of a fine particle and a toner, color restoration is possible by a freezing step. Also, in view of the fact that a melting temperature of the fine particle and a melting temperature of the toner binder can be individually designed, the following relationship can be relatively easily satisfied.(Toner fixing temperature)<(Toner color erasing temperature)
However, by cooling the image to a prescribed temperature, color redevelopment is possible. For example, in a material which undergoes color redevelopment at a temperature relatively close to room temperature, the application is not substantially achieved. For that reason, when the color erasing agent is not used, there was involved such a problem that material types which can be used for the toner are limited.